BackgroundIn the context of the COVID-19 pandemic, physical activity cannot continue to play a role in promoting interpersonal relationships and enhancing social connectedness,people’s contact with the outside world has turned to SNS. During isolation, Whether sharing physical activity experience on SNS can enhance individual social connectedness and its mechanism. The objective of the present study was to examine the associations between sharing physical activity experience on SNS, positive self-presentation, positive feedback ang social connectedness during isolation.MethodsBased on the physical activity experience sharing scale, social connectedness scale, positive self-presentation scale and online positive feedback scale, 460 valid questionnaires were collected online from 31 provinces, municipalities and autonomous regions in China. A series of multiple linear regression models were established to study the relationship between variables, and the bootstrap confidence interval was selected to test the mediating effect.ResultsDuring isolation, sharing physical activity experience is positively associated with social connectedness (b =0.308, p < 0.001), it is also positively associated with positive self-presentation(b =0.956, p < 0.001)and positive feedback(b =0.421, p < 0.001). In addition, it is verified that positive self-presentation has a significant positive impact positive feedback (b = 0.563, p <0.001). positive self-presentation(b =0.331, P < 0.001) and positive feedback(b =0.311, P < 0.001) are positively associated with social connectedness. Finally, it was verified that sharing physical activity experience indirectly through positive self-presentation (b=0.316, 95% CI: [0.180, 0.463]) and positive feedback (b= 0.131, 95% CI: [0.063, 0.207]) also had a significant impact on social connectedness, respectively. and indirectly through the mediation chain of online positive self-presentation and positive feedback (b=0.167, 95% CI: [0.088, 0.251]) also has a significant impact on social connectedness.ConclusionsDuring the COVID-19 pandemic, sharing physical activity experience on SNS can create a positive, healthy and energetic personal image, gain recognition from others, and establish new interpersonal relationships. At the same time, in addition to advocating home-based exercises, governments should encourage residents to share content of home-based exercise or virtual sports on SNS.